Excellent reasoning! Any of the other players would make the plane too heavy for a safe flight, and nothing makes The Captain more angry than pilots who endanger her plane. So, let's review your thinking:

Add the 125 pound player and the 150 pound player together and you get 275 pounds of player.

Subtract that 275 pounds of player from the 400 pounds that can be loaded safely onto your plane and you have 125 pounds, which is the weight of the player you let onboard.